The invention relates to an eddy current reduction braking system, which increases both heat dissipation and braking torque.
In a magnet type eddy current reduction apparatus disclosed in Japanese Patent Publication No. 3-86,050 Publication or the like, a magnet supporting tube is reciprocated in an axial direction to switch between braking and non-braking conditions. Such apparatus has the inherent disadvantage of increasing space requirements in the axial direction.
In a magnet type eddy current reduction apparatus disclosed in Japanese Patent Publication No. 7-118,901, a movable magnet supporting tube is rotated to adjust the relative polarities of magnets axially adjacent in a pair of axially aligned magnet arrays to switch between braking and non-braking conditions. In such an apparatus, however, each pair of N and S-poles of each magnet are directed in a radial direction of the brake drum. It is therefore necessary to process outer and inner surfaces of the magnets into cylindrical or circular form so that an effective magnetic flux is applied to the brake drum via a ferromagnetic plate. The required magnet processing considerably increases cost. Furthermore, the ferromagnetic plates must be large so as to completely cover the magnets in the braking condition. Complete covering by the plates allows the magnets to apply a magnetic field to the brake drum without any substantial leakage. Magnetic flux density cannot be effectively increased to improve braking force therefor due to ferromagnetic plate limitations.
The object of the present invention, therefore, is to provide an eddy current reduction apparatus which is compact in its entirety, and in which braking performance is enhanced.